CN102387629B - Luminous unit driving circuit and light-emitting device - Google Patents

Abstract

The invention relates to a light emitting unit drive circuit and a light emitting device. The light-emitting unit driving circuit provided according to the embodiment of the present invention includes a working voltage supply unit, which provides a voltage input for the driving circuit; a driving unit, which is coupled to the working voltage supply unit, and is configured to drive the light-emitting unit so that the light-emitting unit turn on or off; and a feedback control unit, which is coupled between the driving unit and the light emitting unit, forms a feedback loop together with the driving unit and the light emitting unit, and is used to stabilize the working current of the light emitting unit.

Description

Light-emitting unit drive circuit and light-emitting device

technical field

The invention relates to the lighting field, in particular to a light-emitting unit drive circuit and a light-emitting device.

Background technique

At present, in terms of driving light-emitting units, low-end applications usually use resistors connected in series with several light-emitting units to drive the light-emitting units (for example, LED 1 to LED N), as shown in Figure 1. Such solutions make the output current change with the input voltage, resulting in unstable or flickering LED brightness. In high-end applications, pulse width modulation dimming ICs (PWM ICs) are often used, such as buck circuits and boost circuits. Such schemes are expensive and have complex circuit structures.

In addition, in terms of soft turn-on/soft turn-off of light-emitting units, in some early applications using incandescent lamps, thermal inertia (thermal inertia) was used to achieve soft turn-on/soft turn-off. At present, a programmable microcontroller is often used to adjust the PWM control signal to realize the soft turn-on/soft turn-off function, and the cost of such a solution is relatively high.

In addition, in terms of light-emitting unit dimming, controllable PWM ICs are generally used, and external logic signals are used for dimming. Because additional control signals are required, the system design is more complicated and the cost is higher.

Contents of the invention

A brief overview of the invention is given below in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical parts of the invention nor to delineate the scope of the invention. Its purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

Based on the above problems, there is an urgent need for a solution that can provide a constant output current for different input voltages. The inventors of the present invention propose a driving circuit for a light emitting unit, which solves at least one problem in the above-mentioned prior art, and has a simple structure and low cost.

According to an embodiment of the present invention, a light-emitting unit driving circuit is provided, which may include a working voltage supply unit that provides a voltage input for the driving circuit; a driving unit that is coupled to the working voltage supply unit and is configured to drive the light-emitting unit to making the light-emitting unit turn on or off; and a feedback control unit, which is coupled between the driving unit and the light-emitting unit, forms a feedback loop with the drive unit and the light-emitting unit, and is used to stabilize the working current of the light-emitting unit.

According to a preferred embodiment of the present invention, the driving circuit may further include a dimming unit coupled between the light emitting unit and the feedback control unit and configured to adjust the current level of the feedback control unit to dim the light emitting unit.

According to a preferred embodiment of the present invention, the drive circuit may further include: a switch unit and a soft-on/soft-off setting unit, which are sequentially coupled in series between the operating voltage supply unit and the drive unit, wherein the switch unit controls the soft-on/off setting unit. The soft-off setting unit works in the soft-on setting state or the soft-off setting state, and is used to control the soft-on or soft-off of the light-emitting unit.

Preferably, the drive unit may be configured to include a first transistor, the collector of which is connected to the positive input terminal of the working voltage supply unit, the emitter is connected to the light emitting unit, and the base is connected to the feedback control unit through a first base resistor. The first control terminal is connected to the positive input terminal of the working voltage supply unit through an input resistor.

Preferably, the feedback control unit may be configured to include a second transistor, the collector of which is used as the first control terminal and connected to the base of the first transistor through a first base resistor, and the emitter is connected to the reverse input of the working voltage supply unit end, the base is connected to one end of the dimming resistor through the second base resistor, and the other end of the dimming resistor is connected to the reverse input terminal of the working voltage supply unit, wherein the first transistor, the first base resistor, the second transistor The feedback loop formed by the second base resistor and the light emitting unit is configured to stabilize the working current of the light emitting unit.

As a preferred embodiment, the driving unit can be configured to include a first transistor, the collector of which is connected to the positive input terminal of the working voltage supply unit, the emitter is connected to the light emitting unit, and the base is connected to the soft-turn-on through the first base resistor. The first setting terminal of the soft-off setting unit.

Preferably, the soft-on/soft-off setting unit can be configured to include a soft-on setting loop composed of a soft-on setting resistor and a shared soft-on/soft-off setting capacitor, and a soft-on setting circuit composed of a soft-off setting resistor and the soft-on /Soft-off setting capacitor constitutes a soft-off setting loop, wherein in the soft-on setting loop, the soft-on setting resistor is connected between the first setting end of the soft-on/soft-off setting unit and the switch unit, and the switch unit The other end is connected to the positive input end of the working voltage supply unit, and the soft-on/soft-off setting capacitor is connected between the first setting end and the second control end of the feedback control unit; in the soft-off setting loop, the soft-off The off setting resistor is connected between the first setting terminal and the reverse input terminal of the working voltage supply unit.

As another preferred embodiment, the feedback control unit may be configured to include a second transistor, a diode and a second base resistor, and the collector of the second transistor is connected to the soft-on/soft-off setting unit through the second collector resistor. The second setting terminal, the emitter is connected to the reverse input terminal of the working voltage supply unit, the base is connected to the reverse terminal of the diode, the forward terminal of the diode is connected to one end of the second base resistor, and the second base resistor The other end is connected to the dimming control output terminal of the dimming unit, the working voltage input terminal of the dimming unit is connected to the reverse input terminal of the working voltage supply unit, the dimming unit is connected to the light-emitting unit from the dimming input terminal, and the second transistor The base of the second control terminal is also connected to the soft-on/soft-off setting capacitor of the soft-on/soft-off setting unit, wherein the diode is configured to prevent the soft-on/soft-off setting capacitor from discharging through the second base resistor .

Preferably, the dimming unit can be configured as a variable resistor connected between the light emitting unit and the reverse terminal of the working voltage supply unit for adjusting the working current of the feedback control unit to dim the light emitting unit.

According to another aspect of the present invention, a light emitting device is provided, which may include at least one light emitting unit and the above driving circuit, where the driving circuit is used to drive the at least one light emitting unit to work.

Preferably, the above-mentioned light emitting unit may be an LED.

For any input voltage, the drive circuit provided by the embodiment of the present invention can realize a stable constant current output through feedback control, which is simpler in structure and significantly lower in cost than the PWM solution in the prior art.

In addition, according to the embodiments provided by the present invention, the functions of soft turn-on and soft turn-off of the light emitting unit can be realized on the basis of constant current output, which makes human eyes feel more comfortable.

In addition, according to the embodiments provided by the present invention, the light-emitting unit can be adjusted simultaneously on the basis of constant current output.

In addition, according to the embodiments provided in the present invention, the light-emitting unit can be dimmed while realizing the constant current output function and the soft-on and soft-off functions of the light-emitting unit.

Description of drawings

The above and other objects, features and advantages of the present invention will be more easily understood with reference to the following description of the embodiments of the present invention in conjunction with the accompanying drawings. In the drawings, the same or corresponding technical features or components will be indicated by the same or corresponding reference numerals. The accompanying drawings, together with the following detailed description, are incorporated in and form a part of this specification, and serve to further illustrate the preferred embodiment of the invention and explain the operation and advantages of the invention. In the attached picture:

Fig. 1 is a schematic diagram of a driving circuit of a light emitting unit in the prior art;

2 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention;

3 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention;

4 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention;

5 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention;

6 shows a circuit diagram of a light emitting unit driving circuit according to an embodiment of the present invention;

7 shows a circuit diagram of a light emitting unit driving circuit according to an embodiment of the present invention; and

Fig. 8 shows a circuit diagram of a light emitting unit driving circuit according to an embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in this specification. It should be understood, however, that in developing any such practical embodiment, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and those Restrictions may vary from implementation to implementation. Moreover, it should also be understood that development work, while potentially complex and time-consuming, would at least be a routine undertaking for those skilled in the art having the benefit of this disclosure.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the Other details not relevant to the present invention are described.

Light-emitting unit drive circuit

first embodiment

Various embodiments of the present invention are described below in conjunction with the accompanying drawings. Fig. 2 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention. In FIG. 2 , the driving circuit 200 includes a working voltage supply unit 201 , a driving unit 204 , a light emitting unit 206 and a feedback control unit 208 . The working voltage supply unit 201 provides a voltage input, such as a DC input, for the driving circuit 200 . The driving unit 204 is coupled to the working voltage supply unit 201 and is configured to drive the light emitting unit 206 , such as an LED, so that the light emitting unit 206 is turned on or off. The feedback control unit 208 is coupled between the driving unit 204 and the light emitting unit 206, and forms a feedback loop together with the driving unit 208 and the light emitting unit 206 to stabilize the working current of the light emitting unit.

The working process of the driving circuit 200 will be described below with reference to FIG. 2 . During this working process, the constant current output of the light emitting unit 206 is realized through the closed loop formed by the driving unit 204 , the feedback control unit 208 and the light emitting unit 206 . Specifically, after the working voltage supply unit 201 provides a voltage input, the current passes through the driving unit 204 , so that the current flowing through the light emitting unit 206 rises. Next, the current flowing through the light emitting unit 206 flows into the feedback control unit 208, so that the feedback control unit 208 starts to work. The feedback control unit 208 pulls down the current flowing into the driving unit 204 , so that the driving unit 204 stops working, thereby reducing the current flowing into the light emitting unit 206 . In this case, since the current in the light emitting unit 206 drops, the feedback control unit 208 stops working. At this time, the feedback control unit 208 no longer pulls down the current flowing into the driving unit 204, so that the current flowing into the driving unit 204 increases, and the driving unit 204 starts to work, so that the current of the light emitting unit 206 rises again. In this way, the constant current output of the light emitting unit 206 is realized through the above current circulation.

second embodiment

The above-mentioned first embodiment realizes constant current output. As a preferred implementation of the above-mentioned first embodiment, an implementation of dimming the light emitting unit while outputting a constant current is described below with reference to FIG. 3 . Fig. 3 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention. In FIG. 3 , the driving circuit 300 includes a working voltage supply unit 301 , a driving unit 304 , a light emitting unit 306 , a feedback control unit 308 and a dimming unit 307 . The dimming unit 307 is coupled between the light emitting unit 306 and the feedback control unit 308 and is configured to adjust the current level of the feedback control unit 308 so as to dim the light emitting unit 306 . Wherein the working voltage supply unit 301, the driving unit 304, the light emitting unit 306 and the feedback control unit 308, for example, may have the same or similar features as the working voltage supply unit 201, the driving unit 204, the light emitting unit 206 and the feedback control unit 208 shown in FIG. structure and function. For the sake of brevity, details are omitted here.

The dimming process of the dimming unit 307 is described below. After the working voltage supply unit 301 provides a voltage input, the current passes through the driving unit 304 , so that the current flowing through the light emitting unit 306 rises. Next, the current flowing through the light emitting unit 306 flows into the dimming unit 307 . By adjusting the dimming unit 307, the magnitude of the current flowing into the feedback control unit 308 can be controlled, so that the feedback control unit 308 starts to work. The feedback control unit 308 pulls down the current flowing into the driving unit 304 , so that the driving unit 304 stops working, thereby reducing the current flowing into the light emitting unit 306 . In this case, since the current in the light emitting unit 306 drops, the feedback control unit 308 stops working after the current passes through the dimming unit 307 . At this time, the feedback control unit 308 no longer pulls down the current flowing into the driving unit 304, so that the current flowing into the driving unit 304 increases, and the driving unit 304 starts to work, so that the current of the light emitting unit 306 rises again. In this way, the constant current output of the light emitting unit 306 is realized through the above current circulation. At the same time, since the current flowing into the feedback control unit 308 can be controlled by the adjustment unit 307 , the current change in the above-mentioned cycle is controlled, and the dimming process of the light emitting unit 306 is realized.

third embodiment

In the light-emitting unit drive circuit, in addition to the requirement to achieve constant current output, in order to give users a soft lighting experience, it is hoped that the light-emitting unit can be softly turned on and off. That is to say, after the switch works (for example, turning on or turning off), the current flowing through the light emitting unit (for example, LED) has a change curve without abrupt changes. In other words, when the switch is turned on and off, the light of the light-emitting unit will change softly instead of abruptly, which makes the human eyes feel more comfortable.

An implementation manner of realizing the soft turn-on/soft turn-off function of the light emitting unit is described with reference to FIG. 4 . Fig. 4 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention. The driving circuit 400 includes a working voltage supply unit 401 , a switch unit 402 , a soft-on/soft-off setting unit 403 , a driving unit 404 , a light emitting unit 406 and a feedback control unit 408 . The switch unit 402 is coupled between the working voltage supply unit 401 and the driving unit 404 . The soft-on/soft-off setting unit 403 is coupled between the switch unit 402 and the driving unit 404 . The switch unit 402 controls the soft-on/soft-off setting unit 403 to work in the soft-on setting state or the soft-off setting state. The working voltage supply unit 401, the driving unit 404, the light emitting unit 406 and the feedback control unit 408 may have the same or similar structure as the working voltage supply unit 201, the driving unit 204, the light emitting unit 206 and the feedback control unit 208 shown in FIG. and function. For the sake of brevity, details are omitted here.

The working process of realizing the soft turn-on/soft turn-off of the light emitting unit 406 through the soft turn-on/soft turn-off setting unit 403 is described below. After the switch unit 402 is closed, the energy storage element in the soft-on/soft-off setting unit 403 stores charge for charging. Due to the shunting of the working current due to charging, with the increase of the charging amount, the input current of the driving unit 404 rises in a curve, and the output current of the driving unit 404 also rises in a curve, so that the current flowing through the light emitting unit 406 also rises in a curve , realizing the soft turn-on of the light emitting unit 406 . The time constant determined by the charging loop of the energy storage element determines the rate at which the lighting unit 406 is soft turned on. After the above-mentioned current cycle, the driving circuit 400 enters into a stable working state, and the constant current output of the light emitting unit 406 is achieved. After the switch unit 402 is turned off, the power stored in the energy storage element in the soft-on/soft-off setting unit 403 maintains the input current of the drive unit 404, so that the output current decreases in a curve, so that the current flowing through the light-emitting unit 406 The curve also decreases, realizing the soft shutdown of the light emitting unit 406 . At the same time, the energy storage element is discharged through the discharge circuit, and the time constant determined by the discharge circuit determines the rate of soft shutdown.

Fourth Embodiment

The above-mentioned third embodiment describes a preferred embodiment for further realizing the function of soft turn-on/soft-off on the basis of the second embodiment. Next, a fourth embodiment further having a dimming function will be described with reference to FIG. 5 . Fig. 5 shows a block diagram of a light emitting unit driving circuit according to an embodiment of the present invention. In FIG. 5 , the drive circuit 500 includes an operating voltage supply unit 501 , a switch unit 502 , a soft-on/soft-off setting unit 503 , a drive unit 504 , a light-emitting unit 506 , a feedback control unit 508 and a dimming unit 507 . The dimming unit 507 is coupled between the light emitting unit 506 and the feedback control unit 508 and is configured to adjust the current level of the feedback control unit 508 so as to dim the light emitting unit 506 . The structure and function of the working voltage supply unit 501, the driving unit 504, the light emitting unit 506 and the feedback control unit 508 may be the same as those of the working voltage supply unit 201, the driving unit 204, the light emitting unit 206 and the feedback control unit 208 shown in FIG. Same or similar function. The structure and function of the dimming unit 507 may be the same or similar to those of the dimming unit 307 shown in FIG. 3 , for example. For example, the structure and function of the soft-on/soft-off setting unit 503 may be the same as or similar to that of the soft-on/soft-off setting unit 403 shown in FIG. 4 . For the sake of brevity, details are omitted here.

The following describes how the driving circuit 500 implements the functions of constant current output of the light emitting unit, dimming of the light emitting unit, and soft turn-on/soft turn-off with reference to FIG. 5 . The working voltage supply unit 501 provides a voltage input for the driving circuit 500 . After the switch unit 502 is closed, the energy storage element in the soft-on/soft-off setting unit 503 stores charge for charging. As the charging capacity increases, the input current of the driving unit 504 rises in a curve, and its output current also rises in a curve, so that the current flowing through the light emitting unit 506 also rises in a curve, realizing the soft turn-on of the light emitting unit 506 . After the above-mentioned current cycle, the driving circuit 500 enters into a stable working state, and the constant current output of the light emitting unit 506 is achieved. During the current cycle, as mentioned above, the current flowing into the feedback control unit 508 can be controlled by adjusting the dimming unit 507 , thereby controlling the current change in the above cycle and realizing the dimming process of the light emitting unit 506 . After the switch unit 502 is turned off, the power stored in the energy storage element in the soft-on/soft-off setting unit 503 maintains the input current of the drive unit 504, so that the output current decreases in a curve, so that the current flowing through the light-emitting unit 506 The curve also decreases, realizing the soft shutdown of the light emitting unit 506 .

Fifth Embodiment

Four implementations of the present invention are described above with reference to FIG. 2 to FIG. 5 . A specific example of the above-mentioned implementation manner is described below in conjunction with a specific circuit example. FIG. 6 shows a circuit diagram of a light emitting unit driving circuit 600 of this example. The driving circuit 600 includes a working voltage supply unit 601 , a driving unit 604 , a feedback control unit 608 and a light emitting unit 606 . It should be noted that FIG. 6 only shows a specific implementation provided according to the embodiment of the present invention. Those skilled in the art can implement various alternative implementation modes of the present invention according to the functional block diagrams of the embodiments of the present invention and in combination with the prior art in the field mastered by them.

The working voltage supply unit 601 can provide a DC input, for example. If an industry-standard AC-DC conversion module is added, the working voltage supply unit 601 can also be expanded to generate a DC voltage to be provided based on an AC input. The driving unit 604 may include a first transistor Q1, the collector of the first transistor Q1 is connected to the positive input terminal DC in+ of the working voltage supply unit 601, the emitter is connected to the light emitting unit 606, and the base is connected through the first base resistor R3 To the first control terminal Ctrl1 of the feedback control unit 608 (here, the collector of the second transistor Q2 can be set as the first control terminal Ctrl1) and connected to the positive input terminal DC in+ of the working voltage supply unit 601 through the input resistor R1 . The first transistor Q1 may be a bipolar power transistor, which is used as a linear amplifier transistor by utilizing its characteristic of working in a linear amplifier region. The input resistor R1 is used to determine the operating point of the first transistor Q1.

The feedback control unit 608 may include a second transistor Q2, the collector of the second transistor Q2 is used as the first control terminal and connected to the base of the first transistor Q1 through the first base resistor R3, and the emitter is connected to the reverse side of the working voltage supply unit. To the input terminal DC in-, the base is connected to one end of the resistor R5 through the second base resistor R6, and the other end of the resistor R5 is connected to the reverse input terminal of the working voltage supply unit. The turn-on and turn-off of the second transistor Q2 controls the current flowing into the base of the first transistor Q1, thereby controlling the turn-on and turn-off of the first transistor Q1. The second transistor Q2 may be a small-package signal transistor, for example, its turn-on and turn-off characteristics are used as a base control transistor of the first transistor Q1. The second base resistor R6 is used to determine the operating point of the second transistor Q2.

The feedback circuit composed of the first transistor Q1 combined with the second transistor Q2, the first base resistor R3 and the second base resistor R6 makes the output terminal of the driving circuit output a constant current, and at the same time consumes excess energy of the working voltage supply unit 601, because The voltage provided by the working voltage supply unit 601 must be higher than the voltage of the light emitting unit 606 .

The working process of the driving circuit 600 to realize the constant current output of the light emitting unit will be described in detail below with reference to FIG. 6 . After the working voltage supply unit 601 provides a voltage input, the input current passes through the input resistor R1 to increase the base current flowing into the first transistor Q1, so that Q1 is turned on, and then the light emitting unit 606 (for example, LED) starts to emit light. When the current flowing through the resistor R5 increases enough, the current flowing into the second transistor Q2 through the second base resistor R6 increases, so that the second transistor Q2 is turned on. The current at the collector of the second transistor Q2 increases, thereby pulling down the current flowing into the base of the first transistor Q1, so that the current flowing into the base of the first transistor Q1 through the first base resistor R3 decreases, and the first transistor Q1 stops conducting . In this case, the current flowing into the light emitting unit 606 decreases, and further the voltage on the resistor R5 decreases, causing the second transistor Q2 to stop conducting. In this way, the second transistor Q2 no longer pulls down the current flowing into the base of the first transistor Q1, so that the base voltage of the first transistor Q1 rises, and the first transistor Q1 is turned on again, so that the current in the light emitting unit 606 rises. So far, the driving circuit 600 has reached a stable working state and realized constant current output.

The resistor R5 in Figure 6 adopts a fixed resistance value. However, as required, the resistor R5 can be replaced with a variable resistor, or another variable resistor can be added to realize dimming of the light emitting unit, which will be described below.

Sixth Embodiment

A specific example of an implementation with a dimming function is described below with reference to FIG. 7 . FIG. 7 shows a circuit diagram of a light emitting unit driving circuit 700 according to a preferred embodiment of the present invention. In FIG. 7 , the driving circuit 700 includes a working voltage supply unit 701 , a driving unit 704 , a feedback control unit 708 , a light emitting unit 706 and a dimming unit 707 . The structure and function of the working voltage supply unit 701, the driving unit 704, the feedback control unit 708, and the light emitting unit 706 may be the same as those of the working voltage supply unit 601, the driving unit 604, the feedback control unit 608, and the light emitting unit 606 shown in FIG. Same or similar function. For the sake of brevity, details are omitted here.

The working voltage input terminal a of the dimming unit 707 can be connected to the reverse input terminal DC in- of the working voltage supply unit 701, the dimming control input terminal c of the dimming unit 707 can be connected to the light emitting unit 706, and the dimming unit 707 The dimming control output terminal b of can be connected to the second base resistor R6 of the feedback control unit 708 . The dimming unit 707 can be implemented as a variable resistor R5'. The variable resistor R5' can be connected in series with the resistor R5 between the light-emitting unit 706 and the reverse terminal DC in- of the working voltage supply unit 701, and is used to adjust the current level of the feedback control unit 708, so as to adjust the light-emitting unit 706. Light. Specifically, after the working voltage supply unit 701 provides a voltage input, the current passes through the input resistor R1 so that the base current flowing into the first transistor Q1 (a specific example of the driving unit 704) increases, so that the first transistor Q1 is turned on, and then, The light emitting unit 706 starts to emit light. When the current flowing through the variable resistor R5' increases enough, the current flowing into the second transistor Q2 through the second base resistor R6 increases, so that the second transistor Q2 is turned on. The current at the collector of the second transistor Q2 increases, thereby pulling down the current flowing into the base of the first transistor Q1, so that the current flowing into the base of the first transistor Q1 through the first base resistor R3 decreases, so that the first transistor Q1 stops conducting. Pass. In this case, the current flowing into the light-emitting unit 706 drops, and the voltage on the variable resistor R5' drops, causing the second transistor Q2 to stop conducting. In this way, the second transistor Q2 no longer pulls down the current flowing into the base of the first transistor Q1, so that the base voltage of the first transistor Q1 rises, and the first transistor Q1 is turned on again, so that the current in the light emitting unit 706 rises. So far, the driving circuit 700 has reached a stable working state and realized constant current output. Here, the turn-on and turn-off current of the second transistor Q2 can be adjusted by adjusting the resistance value of the variable resistor R5', so as to control the turn-on and turn-off current of the first transistor Q1 to realize dimming of the light emitting unit 706 . It should be noted that, compared with traditional dimming circuits, the current flowing through the light emitting unit 706 is not directly adjusted here, but the working voltage of the feedback control unit 708 is adjusted by adjusting the resistance value of the variable resistor R5', that is, the second transistor The turn-on voltage of Q2 adjusts the current flowing through the light emitting unit 706 accordingly, so as to achieve the dimming effect. Therefore, much smaller resistors than traditional dimming resistors can be used, thereby reducing the energy consumption of the resistor itself. Of course, the dimming unit 707 can be integrated into the feedback control unit 708, for example, the resistor R5 and the variable resistor R5' can be combined together to form an alternative variable resistor R5" (not shown).

Seventh Embodiment

On the basis of realizing the constant current output of the driving circuit and dimming the light-emitting unit, how to realize the soft-on/soft-off function of the light-emitting unit will now be described with reference to the circuit example in FIG. 8 . Fig. 8 shows a circuit diagram of a light emitting unit driving circuit 800 according to a preferred embodiment of the present invention. The drive circuit 800 includes a working voltage supply unit 801 , a switch unit 802 , a drive unit 804 , a soft-on/soft-off setting unit 803 , a light emitting unit 806 , a dimming unit 807 and a feedback control unit 808 .

As mentioned above, the operating voltage supply unit 801 can provide a DC input. The switch unit 802 may be a common single-pole single-throw switch SW1, or may be, for example, a push button switch, a paddle switch, or other types of switches. The driving unit 804 includes a first transistor Q1, the collector of the first transistor Q1 is connected to the positive input terminal DC in+ of the working voltage supply unit 801, the emitter is connected to the light emitting unit 806, and the base is connected to the The first setting terminal S1 of the soft-on/soft-off setting unit 803 . Here, a point close to R2 between the first base resistor R2 and the resistor R3 can be set as the first setting terminal S1. The first base resistor R2 is used to determine the operating point of the first transistor Q1.

The soft-on/soft-off setting unit 803 includes a soft-on/soft-off setting capacitor, such as an energy storage capacitor C1, a soft-on setting resistor, such as a charging resistor R1, and a soft-off setting resistor, such as a discharging resistor R4. The energy storage capacitor C1 and the charging resistor R1 form a soft-on setting circuit, and the energy storage capacitor C1 and the discharging resistor R4 form a soft-off setting circuit. The charging resistor R1 is connected between the first setting terminal S1 and the switch unit 802, the other end of the switch unit 802 is connected to the positive input terminal of the working voltage supply unit 801, and the energy storage capacitor C1 is connected between the first setting terminal S1 and the feedback control Between the second control terminal Ctrl2 of unit 808. Here, a point between the base of the second transistor Q2 and the reverse end of the diode D1 (described later) can be set as the second control terminal Ctrl2. The discharge resistor R4 is connected between the first setting terminal S1 and the inverting input terminal DC in− of the working voltage supply unit 801 .

The working voltage input terminal a of the dimming unit 807 can be connected to the reverse input terminal DC in- of the working voltage supply unit 801, the dimming control input terminal c of the dimming unit 807 can be connected to the light emitting unit 806, and the dimming unit 807 The dimming control output terminal b of can be connected to one terminal of the second base resistor R6 (described later) of the feedback control unit 808 . The dimming unit 807 may include a variable resistor R5'. The variable resistor R5' can be connected in series with the resistor R5 between the light emitting unit 806 and the inverting input terminal DC in- of the working voltage supply unit 801.

The feedback control unit 808 includes a second transistor Q2, a diode D1 and a second base resistor R6. The collector of the second transistor Q2 is connected to the second setting terminal S2 of the soft-on/soft-off setting unit at the first control terminal Ctrl1 of the second transistor Q2 through the second collector resistor R3. Here, the first base can be connected to A point between resistor R2 and resistor R3 close to R3 is set as the second setting terminal S2, the emitter is connected to the reverse input terminal DC in- of the working voltage supply unit, and the base is connected to the energy storage capacitor C1 as the second control terminal and The reverse end of the diode D1, the forward end of the diode D1 are connected to one end of the second base resistor R6, the other end of the second base resistor R6 is connected to one end of the variable resistor R5', and the other end of the variable resistor R5' One end can be connected in series with the resistor R5 to the reverse end DC in- of the working voltage supply unit. The function of the diode D1 is to prevent the energy storage capacitor C1 from discharging through the second base resistor R6 when the switch unit 802 is turned off.

The working process of the driving circuit 800 will be described in detail below in conjunction with FIG. 8 . The working voltage supply unit 801 provides a voltage input, such as a DC input, for the driving circuit 800 . After the switch unit 802 is closed, the energy storage element C1 is charged through the input resistor R1 and the second transistor Q2 (base to emitter). Due to the shunt effect of C1 charging, in the process of increasing the charge of C1, the base current flowing into the first transistor Q1 through the first base resistor R2 rises in a logarithmic curve, and its collector rises in a logarithmic curve, so that the current The current passing through the light emitting unit 806 also rises in a logarithmic curve, realizing the soft turn-on of the light emitting unit 806 .

During the soft-on process of the light-emitting unit 806, the voltage on the variable resistor R5' rises, so that the current flowing into the second transistor Q2 through the second base resistor R6 increases, so that the second transistor Q2 is turned on. Therefore, the collector current of the second transistor Q2 increases, and under the pull-down effect of the collector current, the current flowing into the base of the first transistor Q1 through the first base resistor R2 decreases, so that the first transistor Q1 stops conducting. In this case, the current flowing into the light-emitting unit 806 drops, and the voltage on the variable resistor R5' drops, causing the second transistor Q2 to stop conducting. Since the second transistor Q2 no longer pulls down the current flowing into the base of the first transistor Q1, the base voltage of the first transistor Q1 rises, and the first transistor Q1 is turned on again, so that the current in the light emitting unit 806 rises. So far, the driving circuit 800 has reached a stable working state and realized constant current output.

During the current cycle, as mentioned above, the base current of the second transistor Q2 can be controlled by adjusting the dimming unit 807 (that is, the variable resistor R5' here), thereby controlling the current change in the above cycle and realizing Dimming of the lighting unit 806. Of course, the dimming unit 807 can be integrated into the feedback control unit 808, for example, the resistor R5 and the variable resistor R5' can be combined together to form an alternative variable resistor (not shown).

After the switching unit 802 is turned off, due to the existence of the diode D1, the energy storage capacitor C1 is prevented from being discharged through the second base resistor R6, so the power stored in the energy storage capacitor C1 maintains the power of the driving unit 804 (that is, the first transistor Q1). base current. Therefore, the current of the collector of the first transistor Q1 decreases in a logarithmic curve, so that the current flowing through the light-emitting unit 806 also decreases in a logarithmic curve, realizing the soft turn-off of the light-emitting unit 806 . The time constant determined by the storage capacitor C1 and the discharge resistor R4 determines the rate of soft shutdown.

So far, the driving circuit 800 realizes the constant current output of the light emitting unit, soft turn-on/soft turn off, and also realizes the dimming function of the light emitting unit.

It should be noted that if soft turn-on/soft turn-off is not performed, the installation method of the switch unit 802 is not limited, for example, it can be installed at the input end of the working voltage supply unit, or omitted. To realize the soft turn-on/soft turn-off function, the switch unit 802 should be installed in the base input circuit of the first transistor Q1.

In addition, it should be noted that for the transistors Q1 and Q2, NPN transistors are used here. This is just an example, and those skilled in the art can also use PNP transistors, and only need to adjust the circuit structure accordingly. In addition, other types of circuit structures can also be used as long as they can be used as linear amplifiers.

In Figure 8, the values of the resistors and capacitors in the RC loop for realizing the soft turn-on/soft turn-off function are not limited in theory, and can be selected according to specific applications, for example, according to the required soft turn-on/soft turn-off rate. select. For example, assuming that the soft-on time is 1 second and the soft-off time is 0.5 seconds, the resistance and capacitance values are as follows: C1 is 22μF, R1 is 400 ohms, R2 is 500 ohms, R3 is 500 ohms, R4 is 50 thousand ohms. It should be noted that the above-mentioned examples are only illustrative, and the present invention is not limited thereto. Those skilled in the art can design different parameter values according to specific circuit requirements.

Eighth embodiment

As another preferred embodiment, the variable resistor R5' in the dimming unit 807 in FIG. for dimming. Since the working process of the driving circuit 600 only for constant current output and the driving circuit 700 for constant current output and light-emitting unit dimming are respectively described in FIG. 6 and FIG. 7 , for the sake of brevity, no longer repeat.

light emitting device

According to an embodiment of the present invention, there is also provided a light emitting device, which may include at least one light emitting unit and the above driving circuit, where the driving circuit is used to drive the at least one light emitting unit to work.

Preferably, the light emitting unit may be an LED.

Several specific implementation modes for realizing the present invention have been given above, which are intended to illustrate rather than limit the present invention. After presenting the overall idea, the inventor described various implementations in combination with specific circuits. It should be noted that these specific implementations are only illustrative, and those skilled in the art can also use other alternative ways to complete the present invention.

Finally, it should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that an article or device comprising a set of elements includes not only those elements but also includes not expressly included. other elements listed, or also include elements inherent in the article or equipment. Furthermore, without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in an article or device comprising the aforementioned element.

Although the embodiments of the present invention and their advantages have been described in detail with reference to the accompanying drawings, it should be understood that the embodiments described above are only used to illustrate the present invention, rather than to limit the present invention. Various modifications and changes can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention is limited only by the appended claims and their equivalents, and various changes, substitutions and transform.

Claims (9)

1. A light-emitting unit drive circuit, comprising: an operating voltage supply unit, which provides a voltage input for the drive circuit; a driving unit, coupled to the operating voltage supply unit, configured to drive the light emitting unit so that the light emitting unit is turned on or off; and a feedback control unit, which is coupled between the driving unit and the light emitting unit, forms a feedback loop together with the driving unit and the light emitting unit, and is used to stabilize the working current of the light emitting unit, Wherein the drive circuit also includes: A switch unit and a soft-on/soft-off setting unit, the switch unit and the soft-on/soft-off setting unit are sequentially coupled in series between the operating voltage supply unit and the driving unit, wherein the The switch unit controls the soft-on/soft-off setting unit to work in the soft-on setting state or the soft-off setting state to control the soft on or soft off of the light-emitting unit, Wherein the drive unit is configured to include a first transistor, the collector of which is connected to the positive input terminal of the working voltage supply unit, the emitter is connected to the light emitting unit, and the base is connected to the soft-turn-on/transistor through a first base resistor. The first setting terminal (S1) of the soft-off setting unit. 2. The drive circuit as claimed in claim 1, further comprising: A dimming unit, coupled between the light emitting unit and the feedback control unit, is configured to adjust a current level of the feedback control unit to dim the light emitting unit. 3. The driving circuit as claimed in claim 1 or 2, wherein the driving unit is configured to include a first transistor (Q1), the collector of which is connected to the positive input terminal of the operating voltage supply unit, and the emitter is connected to In the light emitting unit, the base is connected to the first control terminal (Ctrl1) of the feedback control unit through the first base resistor (R3) and connected to the positive input terminal of the working voltage supply unit through the input resistor (R1). 4. The drive circuit according to claim 3, wherein the feedback control unit is configured to include a second transistor (Q2), the collector of which is connected to the first control terminal through a first base resistor (R3) as a first control terminal. The base and emitter of a transistor are connected to the reverse input terminal of the working voltage supply unit, the base is connected to one end of the dimming resistor (R5) through the second base resistor (R6), and the other end of the dimming resistor is connected to The reverse input terminal of the working voltage supply unit, wherein the feedback loop formed by the first transistor, the first base resistor, the second transistor, the second base resistor and the light emitting unit is configured to stabilize the working current of the light emitting unit. 5. The drive circuit according to claim 1, wherein the soft-on/soft-off setting unit is configured to include a soft-on setting composed of a soft-on setting resistor and a common soft-on/soft-off setting capacitor loop and a soft-off setting loop composed of a soft-off setting resistor and the soft-on/soft-off setting capacitor, wherein in the soft-on setting loop, the soft-on setting resistor is connected to the soft-on/soft-off setting Between the first setting end of the unit and the switch unit, the other end of the switch unit is connected to the positive input end of the working voltage supply unit, and the soft-on/soft-off setting capacitor is connected between the first setting end and the feedback control unit. Between the second control terminal (Ctrl2); in the soft-off setting loop, the soft-off setting resistor is connected between the first setting terminal and the reverse input terminal of the working voltage supply unit. 6. The drive circuit according to claim 5, wherein the feedback control unit is configured to include a second transistor, a diode and a second base resistor, the collector of the second transistor is connected to the The second setting end (S2) of the soft-on/soft-off setting unit, the emitter is connected to the reverse input end of the working voltage supply unit, the base is connected to the reverse end of the diode, and the forward end of the diode is connected to the second base One end of the pole resistor is connected, the other end of the second base resistor is connected to the dimming control output end of the dimming unit, the working voltage input end of the dimming unit is connected to the reverse input end of the working voltage supply unit, and the dimming unit’s The dimming input terminal is connected to the light-emitting unit, and the base of the second transistor is used as the second control terminal and is also connected to the soft-on/soft-off setting capacitor of the soft-on/soft-off setting unit, wherein the diode is configured as Prevents the soft-on/soft-off setting capacitor from discharging through the second base resistor. 7. The drive circuit according to claim 2, wherein the dimming unit is configured as a variable resistor (R5'), connected between the light emitting unit and the reverse terminal of the working voltage supply unit, for adjusting the The operating current of the control unit is fed back to adjust the light of the light emitting unit. 8. A light emitting device, comprising at least one light emitting unit and the driving circuit according to any one of claims 1-7, the driving circuit is used to drive the at least one light emitting unit to work. 9. The light emitting device according to claim 8, wherein the light emitting unit is an LED.